Quote from: MerleOne on November 22, 2007, 08:09 PM

Quote from: f0dder on November 10, 2007, 11:05 PM

SFFS delta backup probably has to read through the entire file to check which range(s) have changed... that's take some time. But I haven't read up on how it does it, so it's just a guess

SFFS cuts the file in smaller parts, performs CRC on a part, same on the target file, and if CRCs differ, this part is updated, and so on.  When target is on a remote server, CRC is performed locally by a Windows service dedicated, so no big data transfer is required.

Smart - but still requires a lot of processing, compared to filter driver approach.

• Set it and Forget it - I never really need to check on it.  The only time I am reminded that it is running is when it cannot connect to the network drive
• Continuously protects versions of files to allow customers choice of recovery points
• Destination is not in propriatary format.....same format
• Offers to only send the portion of the file that has changed vs. entire file again
• Encrypted and/or Compressed options

Do you have any idea if it does this with the help of a filter driver, or (like SFFS/whatever) by scanning the file for changes?

Use sub-file copy check box
Set sub-file copy for remote backup copies.

Initially, an entire file is copied to the storage areas. When sub-file copy is turned on, and when the file changes, only the changed information is copied to the storage area. The sub-file copies are saved as separate files on the remote storage.

Sub-file copy can significantly reduce the amount of network traffic. However, sub-file copy consumes more processing resource on your computer. The default setting is to use sub-file copy for files larger than 50 MB. If you need to conserve more network resources, you can reduce the size setting so sub-file copy will be used on even smaller files.

Check the box to turn on sub-file copy. In the Use sub-file copy for files larger than: field, specify the file size threshold for using sub-file copy. For files larger than this size, only the changed information is copied to the storage area.

Sub-file copy and versioning
If you configure Tivoli Continuous Data Protection for Files to use sub-file copy, it will create files that contain each file's delta information in your designated storage area. Those files have an FPdelta file name suffix.

To test the sub-file copy functionality the file Sub-file example.txt was modified. This file is larger than 3 MB. Figure 4-23 shows the replicated directory in our HTTP Server Paris. As you can see, we have the original file with 3,208 KB and a delta file with only the modified characters which is only 1 KB. Note that this feature is supported only with remote storage.

To track versions of a file, Tivoli Continuous Data Protection for Files adds a version suffix to the file name of the backup copy. On remote storage, all backup copies contain a version suffix. When a file is deleted on your computer, Tivoli Continuous Data Protection for Files will add a version identifier to the file name of the most recent backup copy on the remote storage.

The most recent backup copy of a file is the active backup copy. Older backup copies of that file are inactive backup copies. Tivoli Continuous Data Protection for Files will delete inactive backup copies of a file first if the storage space limit is reached.

A file that is protected by schedule could change several times during the schedule interval. Only the last version of the file prior to the end of the schedule will be backed up. A continuously protected file is backed up after every change.

Adaptive subfile backup
Traditional storage management techniques have focused on protecting systems that stay in the same place and are always connected to the network. Today, many workers are mobile and/or remote, and keep critical data assets on their mobile computers (laptops) and other wireless devices. Storage administrators need new ways to protect mobile and remote computers with limited access to the infrastructure that serves the rest of the company. Some limitations include being attached to the corporate network with reduced bandwidth, limited connect time, and minimal assistance to perform the backup.

This limited access both increases the criticality of storage management services and limits the applicability of traditional methods and policies. Tivoli Storage Manager helps resolve these problems with its adaptive subfile backup feature, which reduces the amount of data transferred while backing up changed files.

This features enables the backup-archive client to back up only the changed portion of a file, either on byte level or on block level, instead of transferring the whole file to the server every time. The changed file portion is backed up as a differential backup relative to the last complete backup of the file (base or reference file) and it is called delta file. All changes since the last complete backup of the file are included in this delta file. In the case of a restore, this allows for the restore of the whole file by restoring only two sub-file components, one delta file, and the last complete backup of the whole file, the base file.

The decision to base the differential on byte level or block level will be made at the backup of the base file, and it depends on the size of the file. Subfile backup technology is not used for very small files (less than 1 KB in size) or for very large files (bigger than 2GB). If the delta file size exceeds 60 percent of the base file at the last sub-file backup, a new base file will be transferred.

The adaptive subfile backup, as well as the restore of a file consisting of a base file and the delta file, is completely transparent to you as a user. All necessary file data separations or reconstructions happen under-the-covers of the backup-archive client. Also, all other Tivoli Storage Manager features, such as policy management or fault-tolerant backup and restore, still fully apply. Adaptive subfile backup is used for incremental as well as for selective backup. It is aware of multithreading and will work together with client data compression and encryption.

10000 file limit per folder (you can sync up to 10 folder)

it has nothing to do with online storage  (no file is stored on their servers...)
and it DOES sync folder to folder either locally or through the internet 
(it does need the foldershare servers to manage the sync process however)

I can't tell for sure from the MirrorFolder site, but it seems that it does not support bidirectional sync. Is this correct? This is a very important feature as the primary use for me would be to keep my files synchronized across all of my pc's, andhaving them in sync automatically means they are backed up in multiple locations as well.

Synchronization between laptop and desktop computers - You can use MirrorFolder to synchronize files between your laptop and desktop computers using bi-directional automatic synchronization mode.